Collapsible multicorner reflector for ultra high frequency radiant energy



Feb. 28, 195@ F. W. DUNMORE ETAL COLLAPSIBLE MULTICORNER REFLECTOR FOR ULTRA HIGH FREQUENCY RADIANT ENERGY Filed Sept. 2'7, 1946 #194 010 Lrous mvsmons ATTORNEY Patented Feb. 28, 1950 COLLAPSIBLE MULTICORNER REFLECTOR FOR ULTRA HIGH FREQUENCY RADIANT ENERGY Francis W. Dunmore, Rockville, Md., and Harold Lyons, Washington, D. 0.

Application September -27, 1946, Serial No. 699,654

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 2 Claims.

The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes without the payment to usof any royalty thereon in accordance with the provisions of the act of April 30, 1928 (Ch. 460, 45 Stat. L. 467).

This invention relates to a type of multi-cubical corner assembly capable of reflecting ultra high radio frequency radar radiant energy, with the reflecting surfaces arranged to fold into a compact package for shipment and to maintain the small package form until any specified time after launching with a free balloon.

The inner corner of a cube is a good reflector for radar signals but a multiplicity of such corners are required to give strong reflections where long distances are involved. Such a design becomes extremely bulky, making shipment costly and launching with a free balloon very diflicult.

Heretofore no eflicient reflector for radar signals has been available which could be folded into compact form for shipment and which could be launched in this compact form with a free balloon, unfolding to form the reflecting area after the balloon is free of ground obstructions.

The object of our invention is therefore to provide an eflicient reflector for radiant energy such as radar signals which may be easily shipped and readily launched with a free balloon, in a manner that makes it possible to accurately track the path of the balloon with radar, thus determining the wind velocity and direction at all heights traversed by the balloon. The balloon supporting the reflector may also carry a radiosonde, thus a complete set of meteorological data may be obtained.

Briefly, the simplest form of our invention consists of four adjacent hollow half-cubical sections, each having three full sides of electrically conductive material, each adjacent section having two sides in common, the four half-cubes being arranged to fold along a common edge into three parallel adjacent flat sections with one side of each half-cubical section folded diagonally and flattened between the flat sections. Timing means are provided so that when suspended from a balloon, the folded half-cubes may unfold after the lapse of a predetermined length of time measured from the instant of release of the balloon. The above four reflecting elements may be multiplied as desired to form as large a reflecting area as necessary. Twelve cubical corners, 2 ft. by 2 ft., have been found satisfactory. Such a reflecting area, when folded, occupies a space 2 48" x 24" x 1". When open, the overall length of the unit is 13 ft. When made from aluminum foil, it can be made to weigh less than 2% lbs.

Other and further objects of our invention will be apparent from the following detailed description and accompanying drawings. It is expressly understood that these drawings are for the purpose of illustration only, and are not designed for a definition of the limits of our invention.

Referring to the illustrations:

Fig. 1 shows a single collapsible unit, comprising two corner reflectors.

Fig. 2 shows the unit of Fig. 1 in a semi-collapsed position.

Fig. 3 shows a complete assembly of units in the open position giving eight (8) cubical reflectors.

Fig. 4 shows the assembly in a folded position held thus by a timing device.

Fig. 5 shows details of a timing device.

Referring to the drawings more in detail, Fig. 1 shows a folding reflecting element in the open position giving two corner reflectors, one having sides I, 3, 2, I; I, 3, 4, 5; and I, 1,6, 5 and the other having sides I, 3, 4, 5; I, 3, 8, 9; and I, 9, I0, 5. The unit folds along the common edge I, I, 9 and along the diagonal I, 4, of the common side I, 3, 4, 5. The common side I, 3, 4, 5 also folds along the edges I, 3 and I, 5. The sides of each half cube are of aluminum foil, paper backed laminated foil, or other electrically conductive material. The framework supporting the foil may be of balsa wood or other light, rigid material. Preferably, a supporting member (not shown) extends along the diagonal I, 4 of side I,

3, 4, 5. The edges 3, 4 and 4, 5 of side I, 3, 4, 5, preferably, are reinforced to prevent tearing.

Fig. 2 shows the element of Fig. 1 in semi-collapsed position showing the fold along edge I, I, 9; I, 3 and I, 5; and along the diagonal I, 4.

Fig. 3 shows a. complete multi-reflector unit composed of four of the elements shown in Fig. 1 and forming, when open, eight cubical corner reflectors, having sides as follows: l5I2--I3--I6; I5I62I--I9; I6I3--I82I; I6-I3I8--2I; I6I3--I4--II; I6 II-22--2I; I5I6 2I--I9; I9-2I-2423; I6-2I-242ll; IIi--2I24-2ll; I6I'|22-2I; 2I 222524; 242I--26-29; 23-I9--2I-24; 23-24 29--28; 24-2I-26-29; 24-2 I2225; 24-45-30-29; 2429--32--2'I; 3I-32--29--28; 2324-29-28; 24-29-32-2I; 29303332; 2425-3029.

Suitable flexible elements, such as strings, extending between comers I2I3, I9-28, I4-22 and 22-30 are of such length that when the re- 3 flector is open, adjacent panels unfold to form a right-angle, cords l|--I2, "-45, "-46, l|l3, |ll| and "-14 serving to support the complete unit. Point II is attached to the lifting element.

Figure 4 shows the complete reflector 34 in the folded position for shipment or launching. It is held in this position by string 35 which is looped at 31 over plunger 36 of a timing device 38. When plunger 36 moves out of loop 31, the

. string 35 is released and the assembly unfolds.

This operation may be timed to take place at any desired elapsed time from the instant of launching the device. The timing device may be of any form well known to the art. One such form is shown in Fig. 5. Here a cylinder 39 carries a plunger 40 attached to rod 36. The string 35 is looped over the piston rod 35 at 31 between supports 44. A spring 43 tends to move the piston 49 in a direction to bring the rod 36 out of the loop 31. When the device is set, the piston is moved to the left, as by means of operating handle 41 on rod 36, loop 31 is passed over the end of rod 36 which is then returned to the right substantially to the position shown in Fig. 5, filling chamber 46 with air which enters through oneway valve 42 which will not allow air to pass out of the chamber. A small opening ll, the size of which is controlled by valve 45, makes possible the exit of air from 43 at a rate which can be set be valve 45. Thus, by setting valve 45, the time taken for plunger 36 to release string 35 may be controlled.

What we claim is:

1. A collapsible four-element corner reflector of ultra-high frequency radiant energy, comprising a solid rectangular shaped fiat sheet of electrically conductive material having two sides at least twice the length of the other two, a second similar rectangular sheet with one of its longer edges hinged to one of the longer edges of said first rectangular sheet, the other longer edge of said second rectangular sheet being hinged to one of the longer edges of a third similar rectangular sheet; a solid square-shaped sheet of electrically conductive material having sides equal in length to the shortest side of said rectangular sheets, one edge of said square sheet being hinged along the shortest center line of said first rectangular sheet, an adjacent edge being hinged along the shortest center line of said second rectangular sheet, said first square sheet being adapted to be folded along the diagonal meeting the common point of the two hinged adjacent edges of said square sheet; a second solid square sheet similar to said first square sheet, with one edge hinged along the shortest center line of said second rectangular sheet on the face of the said second rectangular sheet opposite to the location of said first square sheet, an adiacent edge of said second square sheet being hinged along the shortest center line of said third rectangular sheet, said second square sheet capable of being folded along the diagonal meeting the common point of the two hinged adjacent edges of said second square sheet, suspension means comprising flexible elements connected to said rectangular sheets substantially at the corners thereof at points so spaced along said flexible elements that when said first rectangular sheet is suspended with its free edge horizontal, the three rectangular sheets will take relative positions by the force of gravity such that said first and said third rectangular sheets will be at right angles to said second rectangular sheet with said first rectangular sheet above and said third rectangular sheet below, and said first, and said second square sheets being unfolded along each of their respective diagonals to form a flat surface.

2. A collapsible four-element corner reflector of ultra-high frequency radiant energy, comprising a series of superposed substantially rectangular sheets of electrically conductive material, each having one pair of opposite edges longer than the other pair of the opposite edges thereof, each of the sheets between the endmost sheets of the series having the alternate longer edges thereof hinged respectively to the juxtaposed similar edges of the next adjacent upper and lower sheets to provide for folding the sheets alternately in opposite directions one upon the other in a compact package, suspension means comprising flexible elements connected to the edges of said sheets at points spaced along said elements for supporting said sheets substantially at right angles to each other when supported by said suspension means, and a plurality of foldable substantially rectangular sheets of electrically conductive material each disposed transversely between a different pair of opposing upper and lower sides of adjacent sheets of said series, each of said foldable sheets being disposed with a pair of its adjacent edges traversing and hinged respectively to the opposing upper and lower sides of the sheets of said series with which it is associated.

FRANCIS W. DUNMORE. HAROLD LYONS.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date D. 143,998 Shreeve Feb. 26, 1946 405,354 Hawk June 18, 1889 1,635,915 White July 12, 1927 2,419,549 Griesinger et a1 Apr. 29, 1947 FOREIGN PATENTS Number Country Date 586,904 Great Britain Apr. 3, 1947 752,128 France Sept. 16, 1933 OTHER REFERENCES Electronic Industries, p ge 113, March 1946. 

